ROLE OF INSECT VECTORS IN VIRUS DISEASE EPIDEMIOLOGY: Case from Nepal k WEL-COME workshop on the seed borne virus diseases of vegetable crops by IPM-IL April 7-9, 2014 Himalaya Hotel, Lalitpur, Nepal. Presented by: RP Mainali, N Dangi, AR Ansari

Introduction An organism capable of transmitting pathogens (viruses, bacteria, phytoplasma and fungi) from one host to another Insect – by feeding on diseased plants by contact-acquire disease causing agents-transmit them to healthy plants (by contact, by contamination through soil or other biological agencies) Both piercing and sucking mouthparts and chewing mouthparts are associated with virus transmission

Introduction contd… Insect orders responsible for transmitting viruses comprises Hemiptera (Aphids, leafhoppers, whiteflies, mealybugs etc.)- transmit 90% of plant diseases Thysanoptera (Thrips) Coleoptera (beetles) Orthoptera (Grasshopper) Dermaptera (earwigs) Among, 850 described plant viruses About half are transmitted by aphids (Main vectors are Myzus persicae, Aphis gossypii and A. cracivora) About one third by leafhoppers Some by mealybugs, whiteflies and thrips (Atwal and Dhaliwal, 2008)

Plant virus diseases, more prevalent and destructive in recent years Introduction contd… Plant virus diseases, more prevalent and destructive in recent years Due to better recognition of virus diseases - lab, capacity building Exchange of plant material from one place to another Distribution of many insect vectors For transmission of viruses – activity of vector and persistence of virus have vital role

Review of Research on Insect Vectors of Plant virus Diseases in Nepal

Virus and virus-like diseases are prevalent in the agricultural importance crop (Dahal 1984, Amatya & Manandhar 1986, Shrestha & Albrechtsen 1989, Dahal 1990, Regmi, 1994). Crop productivity depleted by viruses and virus-like diseases (Dahal et al. 1988, Shrestha & Albrechtsen 1989, Dahal 1990). Insect vector management work started (NARC annual report, 2012).

Aphids (Hemiptera: Homoptera: Aphidoidea) More than 150 species of aphids are reported in Nepal (Thapa, 2000, Joshi & Manandhar 2000, Das and Raychaudhury 1983, Sharma 1981/82, Miyazaki, 1977) Aphids on potato (Solanum tuberosum) transfer six important virus diseases in terai and midhill Potato Virus A (PVA) Potato Virus M (PVM) Potato Carlavirus S (PVS) Potato Potevirus X (PVX) Potato Potyvirus Y (PVY) Potato Leafroll Luteovirus (PLRV) (Akius & Kloos 1990)

Myzus persicae Sulzer ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL Vector Transmitted virus diseases References Myzus persicae Sulzer Potato Potyvirus Y (PVY) Ranjit et al. 1998 Potato Leaf Roll Luteovirus (PLRV) Joshi 1979 PRSV-W, ZYMV, CMV, CABYV in cucurbits Joshi and Manandhar 2000; Dahal et al. 1997; Joshi & Manandhar 2000 Bean Common Mosaic Virus (BCMV) Joshi et al. 1993 Pea Seed-borne Mosaic Potyvirus (PSBMV) Shrestha & Acbreehtsen 1989 Turnip Mosaic Virus in Rayo Pradhanang & Ghimire 1993

Contd… OTHER APHID SPECIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL Vectors Transmitted diseases References Aphids (Hemiptera: Aphidoidae) Remarks Aphis gossypii Glover Cucumber Mosaic Cucumovirus (CMV) Joshi 2003 Papaya Ringspot Potyvirus – watermelon strain (PRSV-W) Dahal 1992 Zuchhini Yellow Mosaic Potyvirus (ZYMV) Joshi & Manandhar 2000 Cucurbit Aphid-borne Yellow Luteovirus (CABYV) Regmi et al. 1997 Citrus Tristeza Virus (CTV) Rymi et al. 2000 Aphis craccivora Koch CMV Cowpea Aphid Borne Mosaic Potyvirus (CABMV) Joshi and Manandhar 2000 Pea seed Borne Mosaic Potyvirus (PSBMV) Joshi et al. 1993 Bean Cammon Mosaic Virus (BCMV) Aulacorthum solani (Kalt.) PVY (Potato virus Y), PLRV, CMV Joshi 1979 Joshi & Manandhar 2000 Acyrthosiphon pisum (Harris) PVY, CMV in cucumber Aphis fabae (Scolopi) PVY, CMV in tomato

Contd… Vectors Transmitted diseases References Brachycaudus helichrysi (Kalt.) PVY, CMV and tomato Joshi 2003 Rhopalosiphum padi (Linn.) PVY, PLRV in potato Joshi 1979 Schizaphis graminum (Rondani) PVY, CMV Joshi & Manandhar 2000 Brevicoryne brassicae (Linn.) CMV, PVY Lipaphis erysimi (Kalt.) TUMV in Rayo Shreshta & Albrecalt Sen 1989 Toxoptera citricidus (Kirkaldy) CTV Knorr and Shah 1971 Toxoptera aurantii (Boyer de Fonscolombe) Pentalonia nigronervosa Coq. Chhirke and Furke diseases in Cardamom Castop 1977 Banana Bunchy Top Virus (BBTV) Ojha 1978, Dahal 1990 Rhopolosiphum maidis Fitch PRS-W, ZYMV Dahal 1992 Barley Yellow Hwert Luteo Virus (BYDR) Sitobion avenae (Fab.) BYDV in Gramminae Thapa 2000

Whiteflies (Hemiptera: Homoptera: Aleyrodidae) Whiteflies, Bemisia tabaci) is reported from Nepal (Vidal et al. 1997, Mainali 2012) WHITEFLIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL Vector Transmitted virus disease References Remarks Bemisia tabaci (Genn.) Tomato Yellow Leaf Curl Geminivirus (TYLCV) Joshi et al. 1997 Incidence in tomato and chilli Okra Yellow Vein Mosaic Virus Shrestha and Albrechtsen 1989 Common in terai and inner terai Tobacco Leaf Curl Geminivirus (TobLCV) NARSC 1989 ; Karna & Chaudhary 1999 Mung Bean Yellow Mosaic Geminivirus (MYMV) Joshi et al. 2000

Leafhopper (Hemiptera: Homoptera: Cicadellidae LEAFHOPPER ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL Vectors Transmitted diseases References Remarks Leafhoppers – Cicadellidae Nephotettix nigropictus (Stal) Rice Dwarf Phytoreovirus (RDV) Omura et al. 1982; John et al. 1979 Pest of rice (Dahal et al. 1997). Nephotettix virescens (Distant) Rice Tungro Bacilliform Badnavirus (RTBV) Dahal et al. 1996 N. virescens associated with tungro disease at Parwanipur (John et al. 1979) Rice Tungro Spherical Waikavirus (RTSV)

Thrips (Thysanoptera: Thripidae) THRIPS SPECIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL Vectors Transmitted diseases References Remarks Thysonaptera: Thripidae (Thrips) Scirtothrips dorsalis Hood Tomato Spotted Wilt Tospovirus (TSWV) known as bud necrosis disease (BND) in groundnut Rao & Waliyar 1988; Shrestha & Albrechtsen 1989; Rao & Rao 1992; Thapa 1997 These Virus transmitting vectors associated with different crops in Nepal (Thapa 1997, Joshi & Manandhar 2000). Thrips tabaci Linderman TSWV known as BND in groundnut Thapa 1997 Thrips palmi Karny

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